The present invention relates generally to networks for communication, and more particularly to a multiple segment network device that includes multiple ports that each sense the speed of a connected device and that couples each device to one of multiple collision domains, where the network device may be stacked with other similar network devices via a common backplane to form a stacked arrangement forming a single repeater domain.
Networks serve the purpose of connecting many different electronic devices such as computers, telecommunications devices, printers, file servers etc., so that expensive computing assets may be shared among many users. Such computing assets include, but are not limited to, data and software including programs, files, local and global directories, and databases, and hardware including computers, printers, facsimile machines, copiers, mass storage media, etc., and any combination thereof.
Various communication protocols and standards for networks have been developed to standardize the way in which data packets are transmitted across the data exchange media of the network. For example, Ethernet(trademark), Token Rings(trademark), Fiber Optic Inter-Repeater Link (FOIRL) and Fiber Distributed Data Interface (FDDI) are some of the commonly known network media standards. Also, each standard has its own baseband transmission rate achievable on an applicable physical medium. Ethernet(trademark) is a shared-media network architecture defined in the Institute of Electrical and Electronics Engineers (IEEE) 802.3 standard, and is currently the most widely used architecture for local-area networks (LANs). Ethernet(trademark) uses both bus and star topologies. The 10Base-T is a physical layer standard based on the IEEE 802.3k specification, which is a baseband 802.3-based Ethernet(trademark) network that operates up to 10 Mbps (megabits per second), and is configured in a star topology.
Another Ethernet(trademark) standard has emerged, referred to as Fast Ethernet(trademark) or 100Base-T Ethernet(trademark), which includes implementations capable of 100 Mbps transmissions speeds and is defined in IEEE 802.3u. 100Base-T covers three media types, which includes 100Base-T4 using four pairs of category 3, 4 or 5 unshielded twisted-pair (UTP) wire, and another twisted-wire pair scheme referred to as 100Base-TX using two pairs of category 5 UTP or shielded twisted-pair (STP) wire. Also, a 100Base-FX scheme is defined for use with fiber optic cables. It is noted that the present disclosure and invention is not limited to any particular communications protocol, communication speed, or standard, and may be applied to other protocols and mediums. For example, fiber optic and Copper Distributed Data Interface (CDDI) systems are also contemplated.
In a star configuration, several nodes or computers are connected together through a common hub, which is otherwise referred to as a repeater in Ethernet(trademark) topologies. A repeater is a hardware device that generally functions at the physical layer of the Open Systems Interconnection (OSI) Reference Model to provide a common termination point for multiple nodes. In particular, a repeater receives data from one node and re-transmits the data to other nodes attached to the repeater. Repeaters usually accommodate a plurality of nodes, such as 4, 8, 12 or more nodes, and some repeaters include connectors for linking to other repeaters. Each node in the network is typically a computer of some type, such as a personal computer (PC), Macintosh, minicomputer, mainframe, or the like, where the computer generally includes a network interface card (NIC) for interfacing the node to the repeater to enable networking capabilities. A node may also be a passive device that does not transmit, such as a printer. In the present disclosure, each node is associated with a network device or data terminal equipment (DTE), where each node generally refers to any source and/or destination of data connected to any network system, such as a LAN or the like.
Presently, there is a trend in network technology towards internetworking or enterprise networking, that is, interconnecting networks of different baseband transmission rates to achieve even greater shared access across a larger number of network stations. A current approach to attaining this objective is to use a 2-port bridge device capable of filtering data packets between different network segments or domains by making simple forward/don""t forward decisions on each data packet it receives from any of the segments to which it is connected. As is understood in the art, these segments may be provided with a structured wiring architecture such that a repeater (or, synonymously, a hub) or a multi-station access unit (MAU) provides a central connection point for wiring the network stations disposed in that domain.
In a conventional configuration, one of the ports of the hub for a domain with one baseband transmission rate is connected to one port of the 2-port bridge device, whereas a second hub for a second domain with the same or a different baseband transmission rate is connected to the other bridge port. As can be readily appreciated by those skilled in the art, at least three separate devices must be interconnected, managed, maintained and serviced in order to provide the conventional internetworking solution. Several disadvantages of this arrangement are readily apparent, including less reliability, expensive maintenance, and sub-optimal usage of form-factor.
Accordingly, it should be appreciated that there has arisen a need for an internetworking system that can operate with segments of different baseband transmission rates in a single integrated device. A device that is capable of switch functions at a higher baseband rate is relatively expensive. Also, if several slower speed devices are connected to a single high speed device, such as a server, much of the high speed switch capability is wasted, resulting in an inefficient design. It is desired to provide a cost effective and efficient network for enabling communication among data devices operating at different communication rates. It is further desired to improve effective management of the network.
A multiple segment network device configured for a stacked arrangement via a common backplane according to the present invention includes a first repeater segment, a second repeater segment, a switch device disposed between the first and second repeater segments that enables communication therebetween within a single logical network domain, and a backplane connector coupled to the second repeater segment to enable extension of the second repeater segment to a common backplane with external devices while maintaining a single repeater domain. The first repeater segment operates at a first transmission rate and the second repeater segment operates at a second transmission rate. In an embodiment described herein, the first repeater segment operates at 10 Mbps and the second repeater segment operates at 100 Mbps and each preferably operates according to Ethernet(trademark).
The switch device may be a learning bridge that filters information between the first and second repeater segments. In this manner, local traffic on the first repeater segment is not forwarded to the second repeater segment thereby reducing the number of collisions and traffic on the second repeater segment and the backplane. Also, traffic on the backplane and the second repeater segment is not forwarded to the first repeater segment unless an address designates a network device coupled via the first segment. Thus, extraneous traffic is reduced on each of the segments.
The switch device preferably learns xe2x80x9csourcexe2x80x9d addresses of devices sending packets coupled via the first network segment. Each address is typically in the form of a media access control (MAC) address, which uniquely identifies each manufactured network device. The switch device forwards each packet with an unknown xe2x80x9cdestinationxe2x80x9d address provided on the first network segment to the second segment. An unknown destination address is an address that is not the same as any previously learned source addresses. The switch device forwards each packet with a known destination address provided on the second repeater segment to the first repeater segment. In this manner, a device coupled to the first repeater segment is able to communicate with any devices coupled to the second repeater segment or coupled via the common backplane within a single logical network, and vice versa.
The multiple segment network device may further include a first repeater device operating at the first transmission rate, a second repeater device operating at the second transmission rate, a plurality of port connectors and a plurality of physical devices, each coupled to a corresponding one of the port connectors, where each physical device detects a network device coupled to the port connector and negotiates transmission rate between the first and second transmission rates. The device further includes adaptive repeater logic coupled to each of the physical devices that couples each physical device detecting a coupled network device to one of the first and second repeater devices based on the negotiated transmission rate. In this manner, each network device or node coupled to a port of the multiple segment device is placed into the proper collision domain according to its operating transmission rate.
The common backplane enables two or more multiple segment devices to be coupled within the same logical network domain or local area network (LAN). The backplane couples each second segment of each repeater into the same repeater or collision domain. The switch devices allow nodes coupled through any of the first repeater segments to communicate via the backplane. Multiple repeater devices may be configured in a managed or unmanaged stack configuration. In a managed stack, one repeater is a managing unit and the remaining repeaters are manageable units. The managing unit is assigned a single MAC address for the entire stack, rather than requiring a MAC address for each segment or each separate collision domain. Two manageable repeaters may be linked via a common backplane into an unmanaged stack. At least one of the two repeaters includes an internal arbiter that arbitrates access of the backplane bus between the two repeaters. In an embodiment described herein, each manageable repeater includes a MASTER/TARGET switch which enables/disables an internal arbiter. The MASTER/TARGET switch of one is set to MASTER and the other is set to TARGET in the unmanaged stack.
Accordingly, it should be appreciated that a system according to the present invention provides an internetworking system that operates with segments of different baseband transmission rates in a single integrated device. The present invention provides a cost effective and efficient network for enabling communication among data devices operating at different communication rates. A network device according to the present invention enables efficient utilization of a higher speed segment while enabling communication among slower devices coupled via one or more slower segments.